Haythornthwaite's Peninsular Uniform Book, Plate 61, text, states, "Grenadiers and Voltigeurs had French distinctions, and fusiliers green, sky-blue, yellow and violet for companies 1-4 respectively. Numerous conflicting versions exist; see Uniforms of the Retreat from Moscow, Plate 24."
Note the aforementioned refers to the 4th, 7th and 9th regiments, which served in Spain.
"Uniforms of the Retreat from Moscow", Plate 24;" states 'fusiliers usually had a ball-tuft' [but the plate shows the French style of uniform with French shako]…It also states that "No general rules can be given due to the large number of regimental variations."; p. 123. Unique variations are detailed for a bugler 16th Regiment, an officer 7th, a private 8th and Volitgeur 12th.
There is more detail such as voltigeurs should wear a moustache and grenadiers both a moustache and side whiskers but fusiliers should be clean shaven; etc.; p.124.
I am going for fusiliers green, sky-blue, yellow and violet for my D of W Peninsular regiments.
I hope this information is of some help.